Plasma confining device



PLASMA CONFINING DEVICE Filed May 17, 1960 INVENTOR ICHEL nououe n ai us QeZEAN-M Patented Aug. 4, 1964 3,143,477 PLASMA CONFINENG DEVICE Jean-Michel Doliqae, Paris, France, assignor to Compagnie Generals tie Telegraphic Sans Fil, Paris, France Filed May 17, 1969, Ser. No. 29,693 Claims priority, application France June 2, 1959 (Zlaims. (Cl. 176--3) The present invention relates to devices utilizing an annular enclosure or vessel within which a plasma of a light element such as deuterium is confined within the interior of the space enclosed by the vessel in order to effectively insulate the plasma from the walls so that the particles of the plasma cannot impinge thereagainst and thereby cause energy losses.

It is known in the prior art that such devices may be utilized as generators of neutrons or neuclear energy if one succeeds in confining the particles during a sufficiently long period of time so that the nuclear reactions due to collisions or impacts between these particles carried at very high temperatures have the time to produce at least as much energy as the plasma loses by reason of the usual losses that incur in such devices such as bremsstrahlung, impingements against the walls of the vessel, contaminations and the like.

One of the most widely used manners for producing such confinement is to place the interior space of the vessel, filled with plasma, within a magnetic field of time constant intensity at every point, of which the lines of force are essentially parallel to the walls from which the plasma must be insulated. It is also conventional in such devices having vessels of linear form to produce toward the extremities of the vessel constrictions of the lines of force, so-called magnetic mirrors or throats of magnetic bottles by means of additional magnetic coils producing a more intense magnetic field at the places of the throats or plugs of the magnetic bottles. These additional windings could be avoided and eliminated in principle if the vessel had an annular shape; for by reason of the closure of the interior space upon itself with the annular shape, i.e., by reason of the endless configuration in that case, the axial movement of the particles entrains only the cyclic circulation thereof and does not signify the escape thereof toward the walls, an escape against which seek to combat the magnetic mirrors in a linear vessel, at least insofar as it refers to the longitudinal escape of the particles. However, it has also been found that in the annular vessel it is also advantageous to provide magnetic mirrors distributed over a certain number of points along the periphery of the tore, precisely to reduce this cyclic circulation in such a manner as to impede the movements of the mass of the plasma as a whole, cyclic movement of which the effects are unfavorable as may readily be demonstrated in practice to the maintenance of high temperatures and the stability of the system.

However, even with an annular vessel provided with magnetic mirrors distributed over a certain number of points along the extent of the annulus, the movement of the plasma as a whole and the instabilities resulting therefrom are not eliminated by reason of the imperfect tightness of the throats of the magnetic bottles connected between each other in such a manner as to form a chapelet closed upon itself, i.e., an endless chapelet.

The present invention aims at improving the tightness in such a manner as to render the movements of the plasma within the inside of each magnetic bottle as autonomous as possible.

It is known that the losses or escapes across the throats of the magnetic bottles which are the underlying cause of the undesirable solidarity of the movements within the different bottles takes place for particles of which the velocity vector forms with the axis an angle smaller than the limit value therefor, which may be expressed as follows:

t9 =sin'" /B /B wherein B designates the intensity of the magnetic field within the region of the mirror and B the same intensity within the central region between two mirrors. There exists, therefore, a decided interest to increase the transverse component of the velocity vector of the particles so that the latter leaves from the cone of escape of which the half-angle at the apex is equal to 0 According to the present invention, this increase in transverse velocity is realized by establishing within the plasma contained at the interior of the annular vessel or enclosure, a pattern of standing transverse hydromagnetic waves, so-called Alfven waves, of which the antinodes are disposed at the levels or area of the mirrors. An alternating vector which is perpendicular to the locus of the centers of the meridian sections of the annular enclosure or vessel, called velocity vector of transport of the mass, is associated with these waves. It is known that such a vector is generated by the Velocity vectors of the particles, and when this vector is transverse, the distribution of particle velocities is modified to the benefit of the transverse velocity vectors which opposes the flow of the plasma through the throats of the magnetic bottles.

According to one embodiment of the present invention, the transverse hydromagnetic waves are generated by applying a high frequency electromagnetic field between a pair of electrodes located face to face at the level or within the area of each mirror.

Accordingly, it is an object of the present invention to provide a confining system for a plasma which effectively increases the tightness of the magnetic confining system and therewith decreases the losses with the systems.

Another object of the present invention resides in the provision of means associated with an annular confining system provided with magnetic bottles which enhances the maintenance of the very high temperatures within the system and therewith the possibility of obtaining nuclear energy due to the impacts and collisions between particles of the plasma.

Still another object of the present invention resides in the provision of an annular confining system for a plasma consisting of particles carried at high temperatures which utilizes, in addition to so-called magnetic bottles, an auxiliary system producing transverse standing hydromagnetic waves to increase the tightness of the system.

A further object of the present invention resides in the provision of a system which effectively minimizes or precludes cyclic movements of the plasma as a whole within a confining space which is of endless configuration.

These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, one embodiment in accordance with the present invention and wherein:

FIGURE 1 is a cross-sectional plan view of one embodiment of a device in accordance with the present invention, and

FIGURE 2 is a cross-sectional view taken along line 22 of FIGURE 1.

Referring now to the drawing, wherein like reference numerals are used throughout the two views thereof to designate corresponding parts, and more particularly to FIGURE 1, reference numeral 1 designates therein a toroidally shaped vessel or enclosure, shown in cross-sectional plan view and made, for example, of Pyrex. A longitudinal magnetic field 3 provided with constrictions in the lines of force at spaced points along the extent of the tore 1 is produce by any suitable known means within the interior of the toroidally shaped enclosure or vessel 1. For example, these means may be constituted by six magnetic coils or windings 2 regularly spaced along the tore 1 which are supplied from suitable sources of power (not shown) insuch a manner as to produce'lines' of force 3 directed in the same direction along the circular axis of the toroidal enclosure 1. The lines of force 3 thereby present constrictions at points 4 thereof located at the level or within the area of the coils 2 and diverge between coils 2 in such a manner as to effectively constitute six magnetic bottles forming. a closed chapelet. Reference numeral 5 designates a conventional pump means and reference numeral 6 a conventional means for I density of said tightened magnetic lines of force.

the admission of'plasma whereby the pump'means and r the means for the admission of the plasma may be of any conventional known construction and are therefore shown only schematically in FIGURE 1 of the drawing. The plasma admitted orsupplied from the plasma supply means 5 is confined within the magnetic bottles by the lines of force 3 thereof.

According to the present invention, a pair of electrodes 7 and 8 is provided at the level of each coil 2 which face one another in the radial direction of the tore 1 and, for example, are encased or embedded in the walls of the vessel or enclosure 1. An electromagnetic field is applied between'each pair of electrodes 7 and 8'by means of a source 9 of suitable construction which is connected to the electrodes 7 and 8 in phase opposition. All the electrodes 7, on the one hand, and all the electrodes 8, on the other, are excited in phase by the same source 9. If the frequency of the source. 9 is suitably chosen, a transverse electromagnetic field is established between each pair of electrodes 7 and 8 which excites within the plasma standing transverse hydromagnetic waves having the antinodes thereof at the levels of the constrictions 4.

Typical numerical values for one practical realization of a device in accordance with the present invention are as follows:

Number of coils 2 6 It is understood, however, that the descriptions and numerical values mentioned hereinabove are only given for purposes of illustration and are not to be construed as a limitation on the present invention since the latter is susceptible of many changes and modifications within the spirit and scope of the present invention as known to a personskilled in the art.

Consequently, as the present invention is susceptible of numerous modifications and changes within the spirit and scope thereof, I do not wish to be-limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. A plasma confining device, comprising a ring-shaped vessel, magnetic field generating means associated with said vessel for establishing on the-inside thereof a magnetic field having lines of force essentially parallel to the 2. A device as claimed in claim 1, wherein said lastmentioned means includes, substantially within the region of each said'rnagnetic mirror, a pair of mutually facing electrodes having their surfaces essentially parallel to the walls of said vessel, and a high frequency source operatively connected with the respec tive electrodes of eachof said pairs for energizing the same in phase opposition.

3. A device as claimed in claim 2, wherein one elec trade of each said pair is connected to another homologous electrode of the other pairs to be energized in phase by said source.

4. A device as claimed in claim 2, wherein said vessel walls are of insulating material, and wherein said electrodes are embedded in said walls.

5. An endless plasma confining device, comprising means-forming an endless confining space, means for producing a magnetic field within the confining device having lines of force provided with periodically spaced constrictions and constituting a chapelet closed on itself of so-called magnetic bottles, and means for increasing the tightness of said magnetic bottles and preventing cyclic movement of the plasma as a whole in said endless confining space including means located substantially within the regions of maximum density of said lines of force for producing standing transverse hydromagnetic waves within said plasma.

6. An endless plasma confining device, comprisingmeans forming an endless confining space, means for producing a magnetic field within the confining device having lines of force provided with substantially periodically spaced constrictions and effectively constituting a chapelet closed on itself of so-called magnetic bottles, and means for increasing the tightness of said magnetic bottles and preventing cyclic movement of the plasma as a whole in the endless confining space including essentially oppositely disposed electrode means located within the areas of maximum density of said lines of force, and means including said electrode means for producing standing transverse hydromagnetic waves within said plasma along said endless confining space.

References Cited'in the fileof this patent UNITED STATES PATENTS OTHER REFERENCES Proceedings of the Second United Nations International Conference on the Peaceful Uses of Atomic Energy, volume 31, United Nations, Geneva, 1958, pages 282-284. 

1. A PLASMA CONFINING DEVICE, COMPRISING A RING-SHAPED VESSEL, MAGNETIC FIELD GENERATING MEANS ASSOCIATED WITH SAID VESSEL FOR ESTABLISHING ON THE INSIDE THEREOF A MAGNETIC FIELD HAVING LINES OF FORCE ESSENTIALLY PARALLEL TO THE WALLS OF SAID VESSEL, MAGNETIC MIRROR MEANS DISTRIBUTED ALONG SAID RING FOR TIGHTENING AT PREDETERMINED SPATIAL INTERVALS THE DENSITY OF SAID MAGNETIC LINES OF FORCE, MEANS FOR FILLING SAID VESSEL WITH PLASMA, AND MEANS FOR ESTABLISHING WITHIN SAID PLASMA A PATTERN OF TRANSVERSE HYDROMEGNETIC WAVES HAVING A STANDING DISTRIBUTION WITH ANTINODES LOCATED SUBSTANTIALLY WITHIN THE PLANES OF MAXIMUM DENSITY OF SAID TIGHTENED MAGNETIC LINES OF FORCE. 